This invention relates to lock assemblies, and particularly those of the type including a shell that receives a core having key-operated tumblers that coact with grooves in the shell. The invention specifically provides a universal plug to replace the conventional core to provide for locking without requiring specific key operation.
The invention finds specific application in a lock of the type shown in U.S. Pat. No. 4,398,405 which issued on Aug. 16, 1983 to George P. Patriquin, and entitled LOCK WITH KEY-CONTROLLED REMOVABLE AND INSTALLABLE PLUG AND KEY FOR SAME. That patent discloses a lock having a plural-grooved shell that receives a core having key-operated tumblers that coact with the grooves in the shell. One of the tumblers is used to retain the core within the shell, and a special control key may be used to actuate that tumbler so as to insert or remove the core from the shell. Thus it is a fairly simple matter to change lock cores, as desired.
The present invention is directed to replacing the core disclosed in the Patriquin patent, with its key-operated tumblers, with a universal core having no tumblers, to be used for locking purposes, not requiring a key for operation, until such time as it is desired to install a particular core with tumblers and requiring its own key for locking and unlocking purposes. Such a universal plug finds application in the installation of a large number of desks and filing cabinets and workstations, for example, all having drawers containing locks, in which, in the final installation, various drawers in a particular area are to be locked and unlocked with the same key. Much advance planning is required if individual locks must be installed at the time the furniture is initially manufactured, prior to shipment for installation at a site. It is much easier if all locks are fitted with universal plugs, which may be operated by hand to lock and unlock drawers, with individual cores having key-operated tumblers being installed only following final assembly of all furniture items at the ultimate site of use. Thus drawers may all be locked for shipment purposes, for example, and locked and unlocked during furniture installation and set-up, with installation of cores having key-operated tumblers at the appropriate time at completion of a project when the furniture items are turned over to the customer for use.
The following patents are representative of locks that include cores having key-operated tumblers:
______________________________________ U.S. Pat. No. Applicant(s) Issue Date ______________________________________ 315,307 W. I. Ludlow 04/07/85 Title: LOCK 1,136,141 A. M. Kelley 04/20/15 Title: PANIC EXIT LOCK 3,089,329 W. J. Kerr 05/14/63 Title: LOCK ASSEMBLY FOR A REFRIGERATED CABINET OR THE LIKE 3,589,152 Dwight W. Glass et al. 06/29/71 Title: CABINET LOCK ASSEMBLY ______________________________________
U.S. Pat. No. 4,094,176 issued June 13, 1978 to Donald R. Hughes and entitled PICK FOR TUBULAR CYLINDER LOCKS simply discloses a lock pick.
U.S. Pat. No. 4,228,873 which issued Oct. 21, 1980 to George L. Nyborg, Jr., and entitled ELEVATOR DOOR SAFETY MECHANISM discloses a lock assembly in which the core may be removed to permit a special tool to be inserted for unlocking purposes. This patent does not suggest the use of a universal plug to replace the core using key-operated tumblers.
U.S. Pat. No. 256,723 issued Apr. 18, 1882 to F. W. Mix, and entitled DRAWER LOCK discloses a hand-operated sleeve which surrounds a core having key operated tumblers, which may be used to lock (but not unlock) a drawer. A universal plug to replace a core having key-operated tumblers, as in the present invention, is not suggested.
The invention will be more completely understood by reference to the following detailed description of a presently preferred embodiment thereof .